1. Field of the Invention
The present invention relates to a threadably engageable fuel tank cap which locks in position on a fuel tank inlet, and which requires a key or other actuating mechanism to enable disengagement and removal of the cap.
2. Description of the Prior Art
In conventional systems for locking a vehicle fuel tank, a lock may either be employed in connection with an access door opening for the fuel tank which covers the cap, or a lock may be associated directly with the cap itself. The former system was previously utilized to a great extent because of the expense associated with the locking mechanism and the desirability of ensuring that the locking mechanism was secured to the vehicle, so that a cap inadvertently left off of the fuel tank by a service station attendant could be more economically replaced. However, with the pressing need for pollution control and with the concurrent need to conserve petroleum based fuels, the usage of vehicle caps with locks directly associated therewith has increased. The advantages of a locking a vehicle cap in this regard revolve around the necessity for a vapor tight seal between the fuel tank inlet and the fuel tank cap. Such a seal is conventionally formed by an O-ring interposed between the fuel tank inlet and the fuel cap. The O-ring prevents gasoline or diesel fuel vapors from escaping from the vehicle tank, thereby aiding in eliminating the escape of unburned hydrocarbons into the atmosphere. Some positive means of sealing the O-ring is required, however, and this has typically been provided by constructing the fuel tank cap and fuel tank inlet for threaded engagement with each other.
Conventional mechanisms for locking vehicle fuel tank caps have suffered from several disadvantages. Conventional fuel tank cap construction involves the necessity for turning a key in a lock in one direction, usually counterclockwise to unlock the cap. The key must thereafter be turned in the opposite direction to lock the cap to the fuel tank inlet. Thus, the cap is usually rotated counterclockwise with the key in the lock and rotated in the opposite direction, also with the key in the lock. This is particularly cumbersome and unwieldly since the fuel tank cap key is typically carried as a part of a key ring, chain or key purse and hence presents a considerable inconvenience in manipulating the cap to threadably loosen and tighten it with keys hanging from the lock. An alternative manner of manipulation is to withdraw the key from the lock subsequent to unlocking the cap, threadably disengaging the cap, filling the tank, and threadably re-engaging the cap with the fuel tank inlet. The key is again inserted to lock the cap in position. This also is inconvenient in that it requires the insertion of the key twice into the lock to complete the procedure.
It is an object of the present invention to provide a self-locking fuel tank cap, which requires but a single key manipulation that can be completed entirely prior to any loosening or tightening of the vehicle tank cap. Thus, when the manipulation of the key is complete the key can be withdrawn. The key thereby does not present a hindrance to rotating the cap nor is there a required reinsertion of the key to effectuate locking.
A further advantage of the present invention, as contrasted with other fuel tank locking caps, is that only four major assemblies are required. The principal components are a tank cover with a key mechanism associated therewith, a lug bolt transversely movable relative to the cover, a biasing spring arrangement, and a central core for threadable engagement with the fuel tank inlet. Other locking fuel tank caps require anywhere from eight to twelve major components.
A further feature of the present invention is the deployment to advantage of a clutch mechanism to allow a vehicle tank cap to be threadably engaged with the tank inlet to a sufficient degree to effectuate sealing of the inlet yet to allow disengagment of the cover from the central core to prevent overtightening. Conventional systems are dependent upon the resistance felt by the individual twisting the vehicle tank cap onto the tank inlet to ascertain when sealing has been effectuated. By utilizing the clutch mechanism of the present invention, subjectivity in determining the proper degree of engagment is eliminated. Rather, the cover can be rotated clockwise to tighten the cap onto the inlet until the clutch mechanism begins to slip. This can be felt by the individual closing the fuel inlet and always occurs at the same upper limit of torsional force between the cover and the central core. Thus, the cap can be systematically and repetitively sealed to the vehicle fuel inlet without damage or danger to the structural components of either.